Syntax Magazine

l\| I f\ Serving Timex-Sinclair

I | | Personal Computers

A PUBLICATION OF THE HARVARD GROUP

VOL. 4 NO.IO

IN THIS ISSUE

ISSN 0273-2696 OCT, 1983

HOW TO BUY A TIMEX COMPUTER

8K programs

D-B-H Conversion . 4

Inventory . 17

MC Graphics Demo... ...14

Mystery Program . 14

Retrace Your Steps..... 9

Stop Auto-RUN . 10

We-They Scorepad . 8

Book Review
Aa Introduction to
YU-.CALC Spreadsheeting

for ZX/TS . 15

Buying by Mail —

Know Your Rights . 6

Classified Ads . 23

Dear Editor . 12

Faster Pseudorandom

Numbers . 10

Hardware Review

Zebra Light Pen . 5

Hardware Tutorial
Addressing — A

Brief Tutorial . 21

New Products and

Services . 2

News . 1,21

Program Improvements .... 3
Software Reviews

ZXMAN . 21

ZX PRO/FILE . 16

Subscription Info . 23

Syntax Error . 2

Timex at the Heart

of the Kidney . 11

Users Groups . 11

Vendor Report . 14

Index of Advertisers

E-Z Key . 16

R.I.S.T . 3

Suntronics . 7

Syntax . 15

Last month we reported you could buy Timex
hardware and software by mail. Timex took
exception to that report. "We do not have a
primary plan to sell computers by mail. The
800-24-TIMEX number provides referrals to
stores," said Timex VP Dan Ross.

"We will arrange to service you (custom¬
ers) by mail — but only after we have directed
you to retail outlets and they have been un¬
able to fill your needs," Ross later clari¬
fied. "We are cleaning up our 800-number
list now to make accurate retail referrals."

"Our primary thrust is to support retail
distribution of Timex Sinclair computers," he
concluded .

1500S ON THEIR WAY, 2068S CLOSE BEHIND

Our Timex source says a few TS1500S began
their way to your local stores the first week
of September. The FCC approved the TS2068
recently; expect it in stores by October.

You can order TS2068s now through Sears'
Christmas catalog — $179.99 less 10% if you
order before 18 Oct. Cat. #3 E 23022C.

TIMEX SINCLAIR CELEBRATION IN BOSTON

To commemorate their 2nd year, the Boston
Computer Society's 800-member Sinclair Timex
User Group will bring together TS owners,
user group reps from all over and hardware,
software, publication and service vendors for
a day-long show and workshops.

Dan Ross of Timex and Maggie Bruzelius
from Sinclair will give updates on each com¬
pany. A local retailer will sell TS1000/1500
and 2068s, plus printers, RAMs, and software.

For info, call Sue Mahoney, 203/755-
2699, Jack Hodgson, 617/354-7899 or BCS, 617/
367-8080. $1 to BCS members, $2 to any UG

member, $3 general and $5 family. Saturday,
22 Oct., 10A-6P, Boston Park Plaza Hotel.

1

SYNTAX ERRORS J. Brezina of Elm¬
hurst, IL, reports to get correct
Puerto Rican and Washington, DC,
zip codes in ZIP-TO-STATE... (Sept,
83), delete lines 5140 and 5150 and
add the following lines. Also,
delete line 5110 (a repetition).

W.C. Andrews of San Anselmo, CA,
sent this correction/improvement:

NEW PRODUCTS AND SERVICES

BIO-RHYTHMS program provides month¬
ly biorhythms and summarizes your
important biorhythmic days. Docu¬
mentation includes theoretical
background. Tape $7.95. UAS, POB
612, Haddonfield, NJ 08033.

New ZX/TS books: The Timex Sin¬
clair 1000 Ideabook by David Ahl,
$8.95; J10 Programs for the Timex
Sinclair by Leland Carter, $6.95.
Creative Computing Press, 1 Park
Ave., NYC, NY 10016, 212/725-7892.

GOLF HANDICAPPER computes, saves,
updates handicaps for up to 48
players. Computes by USGA guide¬
lines for 18-hole courses. 16K
tape w/doc. $20 check or MO to
John B. Carson, Jr., 11200 Lockwood
Dr. #307, Silver Spring, MD 20901.

ZX81 Text Processor, 2000-word ca¬
pacity, edit in full or split¬
screen, 32K. Tape $12.50, check or
MO to A. Rodriguez, 1605 Penn.

Ave., #204, Miami Beach, FL 33139.

DEMONSTRATION demo program for
TS1000/1500, $9.95; PRO-FILE PLUS
data base, $14.95; INTRUDER ALERT
game, $14.95, $1.50 P&H, all 16K,
new from Williamware, 1300 DePaul
Wy, Virginia Beach, VA 23464.

Instant-load plug-in cartridges and
replaceable ROMs for TS1000/1500S,
games, finance, utilities, graph¬
ics, science programs. Also piggy¬
back extender, 2K machine ROMs.
Blank cartridge and any ROM soft¬
ware $25. Extra ROMs $15. SASE
for catalog. ROMPAK, 8206 Black¬
burn Ave., Los Angeles, CA 90048.

The Sinclair ZX81 by Randle Hurley
covers programs, programming tips,
hardware mods. $17.95 (hardcover),
176 pp. TAB BOOKS Inc., Blue Ridge
Summit, PA 17214, 717/794-2191.

1984 MICROCOMPUTER MARKET PLACE
includes 3000 software publishers,
distributors and publications, some
ZX/TS suppliers. Dekotek, 2248
Broadway, New York, NY 10024.

TS2000 books: TS2000 Machine Lan¬
guage for the Absolute Beginner .
TS2000 Hardware Manual. The TS2000
Collection. TS2000 Programmer's
Reference Guide, (by Ian Logan).
$14.95 ea., ppbk. In November:
Complete TS2000 ROM Disassembly.

(by Ian Logan and Frank O'Hara),
$19.95. Melbourne House, Dept. CS,
347 Reedwood Dr., Nashville, TN
37217, MC/VISA 615/361-3738.

Intercontroller computerized con¬
trol system times up to 4 electri¬
cal devices. Each outlet supplies
6A at 110V, 60 Hz. Connect up to 4
Intercontrollers to your ZX/TS.
$99.95+$4.95 S&H. Intercomputer,
Inc., 358 Chestnut Hill Ave.,
Boston, MA 02146, 617/738-5310.

2

QUICKDRIVE utility and graphics
program gives MC routines with
BASIC demo, including BORDER, INPUT
CHECK, SPIRAL, SCROLL. Resides
above RAMTOP at location 31813,
$12.95. MICRO-LOAD, POB 1095,

Truth or Conseq., NM 87901.

TREE-FORTH version of FORTH on 64K
EPROM chip. System $49.95, $2 P&H.
Soft Magic Corp., 1210 W. High St.,
Bryan OH 43506, 419/636-4531.

Get over 40% discount on power
outlet strips, surge suppressors,
transient voltage suppressors.

Free shipping over 12 units, COD
OK. Applied Electronics Resource,
11417 Fairfax Sta. Rd., Fairfax
Sta., VA 22039, 703/281-6056.

RAM-MIT holds computer, RAM; im¬
proves keyboard angle. Acrylic;
predrilled holes to add on/off/re¬
set switch with plug and jacks (RS
switch #275-324, plug #274-286,
jack #274-251. $19.95. Laminar

Inc., Box 12332, 1514 Fairview,
Columbus, OH 43212, 614/488-5158.

Inc ANNOUN

SPEECH

SYNTHESIZER

SALE

*ACT NOW: Receive

Exclusive Phrase Finder Program "$5. VALUE FREE
Speech Synthesis Instruction M.inual ”$10. VALUE FREE
ORDER NOW ORDER NOW

HEAR THE POWER

Mrrcc „

o*v

&

HOW YOU CAN MAKE YOUR COMPUTER TALK.

The PARROT newly introduced by R.I.S.T., gives the
power of speech to Time* /Sinclair Computers. This simple
to use plug-in speech module is capable of generating all the
sounds in the English language. The combination of these
sounds, in the order of your choice, will generate an
unlimited vocabulary of words, phrases, and sentences as
well as an array of sound effects. Piggy-back

expandability allows other modules (eg. memory) to be
[operating with the Parrot simultaneously.

>aul Donnelly had this to say in the April issue of Syntax:

"Documentation is professional..."

"Overall, R.I.S.T.'s Parrot is an excellent unit and per
orms up to and behond my expectations."

- i

SALE

Send To: R.I.S.T. Inc
Dept. 21 (Fomerly
Voicetech)

P.O. Box 499, Ft
Hamilton Station

Brooklyn, N Y.
11209 - (212) 259-4934

Please send me f _

Parrot(s) Speech Syn¬
thesizers for my □
ZX80 □ 2X81 D

TS1000 at $59.95 ea. plus
$4.00 sh/hd

I will also receive an exclu¬
sive phrase finder pro¬
gram and a 40 page in¬
struction manual, FREE

15 DAY MONEY BACK
QUARANTEE/C.O.D.
ORDERS ADD $1.75
PAY BY BANK CHECK
OR MONEY ORDER
NY S RESIDENTS
ADD 8%% TAX.

PROGRAM IMPROVEMENTS

Z-WRYTER word processor gives type-
over corrections, works with print¬
ers using TS ROM routines. 12-page
capacity with 16K RAM, usable with
larger RAM. $12.95+$1.25 S&H, $10
Express Mail. Robotec Inc., 59 C
St., Ampoint Industrial Park,
Perrysburg, OH 43551, 419/666-2410.

In November: Games for Your TS1000
by Mark Charlton and Games for Your
TS. 2000 by Peter Shaw. Each offers
over 20 games plus hints for pro¬
grammers. In stores or from Dell
Publishing, POB 1000, Pine Brook,

NJ 07058 (+$0.75 each for P&H).

New programs (five 2K, six 16K)
include games, checkbook balancer,
graphics, math, organizers, tax and
bank records, drink/food recipes,
music and light displays. Prices
$9.95-$14.95. Request free cata¬
log. SIMULUSION, POB 894, Lemon
Grove, CA 92045, 619/263-6591.

Add these lines to SPELLING WORD
GAME (Aug. 83) to help remember the
words you enter. At the first
prompt, type the words to unscram¬
ble (these remain on the screen).

At the second prompt, enter your
scrambled list. At the the third
prompt, reenter unscrambled words.

Edward Sidorski, Susquehanna, PA

Simplify SET RAMTOP AUTOMATICALLY
(Aug. 83) by deleting lines 70-210
and adding line 60:

J. Brezina, Elmhurst, IL

3

D-B-H CONVERSION — 8K/16K

Convert decimal, binary and
hexadecimal numbers easily with
this well prompted utility.

Type in the program and RUN or
GOTO 500. Press D, B or H as
prompted, depending on the number
you wish to convert. Enter numbers
imitating the style as prompted.

For example, you must enter binary
numbers with 16 digits in groups of
four. Your screen looks like this
after you ENTER a number.

Four labeled lines appear; A de¬
fines the address bits of a 16-bit
bus. B expresses the binary value,
grouped in 4-bit clusters. H gives
the translation of each cluster to
its hex equivalent. D shows the
translation to decimal, by byte
(two clusters) and the decimal sum.
When you press S to stop, you see
report code 9/line #. SAVE with
GOTO 900; the program then auto-
RUNs when you LOAD. RUN 500 to
start again. Press C to copy the
screen display; this will not in¬
terrupt program execution.

Kenneth Sell, Long Island City, NY

RETURN

4

HARDWARE REVIEW

Product: Zebra Light Pen

From: Zebra Systems

78-06 Jamaica Ave.
Woodhaven, NY 11421
212/296-2385
Price: $24.95 + $3 P&H

Light pens resemble simple
wands you point at your TV display
to perform many functions usually
invoked with keystrokes. The pens
can sense light and dark screen
areas and use the brightness it
"sees" to help you choose the in¬
formation or area you want.

Typical light pen uses include
menu selection (just point the pen
at your choice) and graphics devel¬
opment (tracing complicated line
drawings onscreen). Other uses in¬
clude game playing (selecting ob¬
jects in an adventure game), and
such esoteric attempts as simple
photocell operation (sensing light
or dark in a room, for example) and
measurement functions (sensing in¬
termittent motion).

Zebra's pen consists of a wand
about 6" long with photocell assem¬
bly. It plugs into a 2"x2" open
board containing input jacks for
the pen and ZX/TS 9V power supply,
output plugs to power your computer
and send the pen's signal to the

EAR port, and hardware to condition
the pen's output. The hardware
includes an LM339 Quad Comparator
hooked up in four separate modes:
comparator, pulse stretcher, oscil¬
lator and output driver. Using a
simple LM339 for all these func¬
tions deserves mention as an out¬
standing design achievement.

Documentation seems brief, but
complete except for lack of sche¬
matics. A cassette with a simple
adjustment procedure on one side
and a fairly involved "Concentra¬
tion" game on the other provides
you with ready-to-run software and
some excellent programming exam¬
ples. Zebra provides an assembly
listing of the light pen's input
routine (17 bytes). You must ad¬
dress the pen as port FE (hex) and
plug it into the EAR jack after you
LOAD your user program. The com¬
puter actually reads only one bit.

I set up my pen without diffi¬
culty and found it worked adequate¬
ly, though slowly for choosing
squares in the Concentration game
and for menu selection. You must
place the pen tip flat against the
screen to get a reliable read.

Complaints: The computer's 9V

power feeds through the unit — a
problem with homemade keyboards
with certain types of internal
power supplies. You must discon¬
nect the plug you used to LOAD the
program and plug the pen output
into your EAR jack — an inconveni¬
ence. My adjustment program con¬
tained a minor mistake.

Despite these flaws. Zebra's
light pen presents a reasonable
buy, especially if you need a mod¬
erately reliable light pen or just
want to experiment. With large
enough blinking blocks, the physi¬
cally handicapped could use this
pen. People unfamiliar with compu¬
ter keyboards could also use it for
applications programs. With its
low resolution, I see no valid
graphics development for the Zebra.

Paul Donnelly, Centerport, NY

5

BUYING BY MAIL — KNOW YOUR RIGHTS

ZX/TS consumers can purchase
many items through the mail. Mail
order shopping can conveniently
save you time and effort. But how
can you know if you will ever re¬
ceive the items you order? Take
the first step — knowing your rights
— to avoid victimization by un¬
scrupulous vendors.

Federal Trade Commission rules
give you some rights when you order
by mail. The FTC adopted the Mail
Order Rule in October, 1975. This
rule states:

* You must receive the merchandise
when the seller says you will.

* The seller must ship the mer¬
chandise to you no later than 30
days after your order arrives if
the seller states no specific de¬
livery time.

* If you don't receive it shortly
after 30 days, you can cancel your
order and get your money back.

Sellers must notify you if a
"first delay" situation exists;
i.e., when the seller cannot meet
the promised delivery date (or the
30-day limit). The seller must
also notify you of the new shipping
date and give you the option to
either cancel the order and receive
a full refund, or agree to the new
shipping date. The seller must
also give you a free way to return
your answer, such as a stamped
envelope or postage-paid post card.
CAUTION! ! ...if you don't answer, it
means that you agree to accept the
shipping delay.

When you cancel a prepaid
order, (unless you paid using your
credit card) , the seller must mail
you a refund within seven business
days. For any additional delays,
the company must obtain your ex¬
press consent. If you cancel a
mail order charged on your credit
card, the seller must credit your
account within one billing cycle
after receipt of your request.

This mail order rule does not apply
to certain purchases such as: mail

order photo finishing, orders for
seeds and plants, magazine sub¬
scriptions and other deliveries in
a series (except for the initial
shipment) , COD orders and credit
orders when you do not charge be¬
fore the company mails the merchan¬
dise. Also, the rule does not
generally apply if you order an
item by phone, perhaps using a
seller's "800" toll-free number.

If you experience a problem
with a mail order purchase, first
contact the mail order company.
Provide your account number, order
number, the exact name or initials
you used when ordering, check num¬
bers, order date, etc. The more
you provide (and keep track of from
the start), the better your chances
for resolution of your problem,
especially when dealing with small
companies that may lack organized
record-keeping systems. If you do
not obtain satisfaction from the
company, contact the following or¬
ganizations for assistance. Keep
copies of all communications.

* Your local or state consumer
protection office or Better Busi¬
ness Bureau.

* The consumer protection agency
nearest to the company.

* Your local postmaster. Ask for
the name and address of the appro¬
priate postal inspector in charge.

* The book, magazine or newspaper
publisher that carried the adver¬
tisement. Publishers often try to
resolve problems between readers
and advertisers. (SYNTAX'S Vendor
Report develops mostly from reader-
supplied information. — LFV)

* The Direct Mail/Marketing Asso¬
ciation, Mail Order Action Line, 6
E. 43rd St., New York, NY 10017.

* The Federal Trade Commission 6th
St. & Pennsylvania Ave., Washing¬
ton, DC 20580.

Although the FTC can't resolve
individual disputes, your informa¬
tion may help reveal patterns of
practices requiring FTC action.

Victor Font, Jr., Jersey City, NJ

6

BEST KEYBOARD AVAILABLE!

For Your

ZX-81 ITS-1 000

□ Includes Shielded Case
□ Fully Warranted For 90 Days
□ Now In Stock

□ Hundreds of Satisfied Customers

LOWER

PRICE

EASY TO

SUN KD-81

If you’re tired of not knowing whether your data got entered or tired of pok¬
ing data in with one or two fingers, then it’s time to upgrade your ZX-81 to
a full size, professional keyboard. The SUN KD-81 KEYBOARD offers all
the ease and comfort of inputting your programs and text on a fast and ef¬
ficient professional-sized keyboard!

KD-81 FEATURES

INSTALL

• No Soldering

• No Modifications

• Full size keyboard with 41 keys expansion module to be plugged

• Two color silk-screened key tops m

for easy reading • Keyboard comes with own cables

• Key tops have commands and • Keyboard case holds both

graphics spelled out the same as keyboard and computer with room
ZX-81 to spare

• Extra shift key for real keyboard- • High impact plastic case with

style typing vaporized metal shielding

• Full size space bar • Easy assembly — no soldering,

• Allows touch typing no modifications

• Rear cutout allows any RAM or * Measures 10%" x Vkn x 2 Vs"

DEALER INQUIRIES WELCOME

GET A BETTER PICTURE WITH SAMWOO MONITORS

SAMWOO provides a much better picture for your Sinclair
Computer than your TV monitor. Simple modification pro¬
cedure includes easy-to-follow instructions.

9" 18Mhz BANDWIDTH 12" 12Mhz BANDWIDTH

reen . $115.00 Green . $124.00

range . 119.00 Orange . 127.00

Add $7.50 Shipping and Handling for this item.

Features:

• Composite Video
Input/Output

• Switchable Input
Impedance 75 or
lOKohm

• 750 Line Resolution
at Center and 500
Lines at Corners

• Dimensions are
12.13" x 11.34" x
11.65" for the 12"
model and 8.66" x
8.54" x 9.05" for the
9" model

Simple installation
steps included
with
each
kit.

RAM MODULES

> Built-in output connector for piggyback

> Up for mounting on ZX-81 & KD-81

> High-impact plastic case with vaporized metal
shielding

> 6.6" wide, 3.2" high, 1.08" deep

16K $49.95 mx-i6kp
RAN $qq nn

swrmics CO., INC.

12621 Crenshaw Blvd., Hawthorne, CA 90250

STORE HOURS: MON.-FRI. 9:00 am to 6:30 pm
SATURDAY 10:00 am to 5:00 pm

CALIFORNIA OUTSIDE CALIFORNIA TOLL FREE

213-644-1149 1-800-421-5775

(for Tech Info and Calif, orders) (Order Desk Only)

Mail Order - Minimum Order $10. Send Money Order or Check. VISA or Mastercard
(please include expiration date). Add $4.00 postage and handling to order. CA residents
add sales tax.

WE-THEY SCOREPAD — 8K/16K

WE-THEY keeps score for two-
person or two-team games.

To use WE-THEY, enter the
program as shown and save by RUN
620. Enter the name of the game,
winning score, whether the total of
each WE-THEY entry must equal a
predetermined value, and verify the
information offered. The scorepad
appears on the screen, displaying
the game name, winning score and a
prompting box. Under the headings
WE and THEY you see the last score
input and the totals.

First input the score for WE,
then THEY. The prompting box waits
for the next entries at game's end.
When someone wins, the scorepad
scrolls offscreen and the winning
score appears. To score a new
game, just press ENTER.

If no one wins after 13 score
entries, the scorepad scrolls off¬
screen and reappears with the cur¬
rent scores and totals listed
again. This ensures the prompt
box, which scrolls with the scor¬
ing, remains onscreen.

Variables:

WT — scoring total for WE
TW — scoring total for THEY
J — controls print position for
prompting box

C — if C=0, the total of WE and THEY
entries need not equal a predeter¬
mined value? if C=9, the total must
meet predetermined value (line 298)
SC — winning score

U — if U=0 then score applies to WE.
If U=l, score applies to THEY
(lines 412, 414)

T — if TO0 , it represents the total
of WE and THEY. Under this condi¬
tion, only scores whose total
equals the predetermined value T
are valid

K — counts number of scoring lines
displayed on screen. When K=13,
scorepad is redrawn and K set to
zero (lines 130, 133)

Line Functions:

100-109 draw scorepad format on
screen

111-128 accept input scores
130-135 redraw display if K=13
295-315 check whether WE plus THEY
must equal a predetermined value,
calculate totals, list scores and
totals on scorepad
400-414 check for unacceptable en¬
tries (characters other than 0-9)
500-542 obtain information at start
of program on nature of game to
score

550-575 display end of game info
600-615 accept answers to YES and
NO questions at start of game
700-705 are a delay routine

Harold Hart, James Park, NB, Canada

8

iNfU •

RETRACE YOUR STEPS — 8K

This program lets you draw on
your screen using arrow keys and
stores your drawing in an array.
Type in the listing, then RUN in
SLOW. Use the arrow keys to move
the square in the lower left cor¬
ner, leaving a line behind.

When you finish, press R. The
computer clears the screen and re¬
traces your steps, then stops. You
can quit early by pressing BREAK.

David Margrave, Missoula, MT

9

FASTER PSEUDORANDOM NUMBERS

I find the RND function rather
slow, especially troublesome when
used in realtime graphics games.

You can sequentially PEEK from the
8K ROM's machine language operating
system (essentially a pseudorandom
number table) from a randomly
selected starting point to provide
"random" numbers. This method
works demonstrably faster than
using RND. RUN the following short
program in SLOW to randomly place
an inverse space in each of the
first 22 screen rows.

Execution time: 4.6 seconds.
Now try this, also in SLOW:

These lines produce the same dis¬
play in 3.5 seconds. Line 1 sets P
equal to a number between 0 and
999. Line 3 PEEKS the address
formed by adding the loop counter I
to P. Address P+I always holds a
number between 0 and 255, so divi¬
sion by 8 gives pseudorandom num¬
bers between 0 and 31. Generate
numbers in any range by picking the
proper division and/or algebraical¬
ly manipulating PEEK (P+I). This
technique usually runs about 25%
faster than using RND repeatedly.

RACER, following, runs in 2K
if you add the following lines to
initially fill the display file.

(It won't fit in IK.) Larger
memories do not need these lines.

Note lines 40, 90 and 100 work to
produce the "winding" of the road.
Use this technique to speed up any
program using RND. Steer the star
down the road using keys Y and 8.

Dan Tandberg, M.D., Albuquerque, NM

STOP AUTO-RUN

Use this program to stop an
auto-RUN program (a program that
automatically RUNS when LOADed)
before it RUNS.

Type in this program and SAVE
it, because your auto-RUN program
wipes it out. With this program
in your computer, put the auto-RUN
tape in your tape deck. Hit RUN
then ENTER. The screen goes blank
for two seconds in FAST, eleven in
SLOW. When a flickering diagonal
pattern appears on your screen
(indicating LOADing) , press PLAY on
your recorder. When your auto-RUN
program has LOADed, a STOP report
code (9/line number) appears in the
bottom left of your screen. Now
hit LIST to see your program.

Lloyd Painter, Quakertown, PA

lO

ZX/TS USERS GROUPS

TIMEX AT THE HEART OF THE KIDNEY

TS1000S plus peripherals can
make life easier and less expensive
for artificial kidney patients and
US taxpayers.

Artificial kidneys used by
dialysis patients cost $20-50 each
and patients can use each only
once. Each kidney patient must
dialyze, using a new kidney, three
times a week. Medicare, through
our tax dollars, bears 80% of this
cost for 64,000 US artificial kid¬
ney patients. At an average of $30
per dialysis, each patient spends
$72 per month personally, while the
government picks up the remainder —
hundreds of millions of dollars for
treatments each year.

So where does our TS1000 fit
in? Medi Products of Salt Lake
City built a system to reclean and
resterilize artificial kidneys
around a TS1000 with a Votem from
Down East Computers, Greenville,

NC, and Persona, Periconb and a
special keyboard from Sinclair
Place, Redmond, WA. The computer
completely controls all processes
under EPROM software direction.

Now kidney patients can use a
single kidney up to six times, cut¬
ting their own costs to about $14
per month and potentially saving
Medicare millions.

Medi Products president Dick
Fife says they expect FDA approval
of the device (priced at $5000)
very soon. For information, con¬
tact Dick Fife at Medi Products,

240 West 2950 South, Salt Lake
City, UT 84115, 801/487-8244.— ALZ

To find a group in your
area, or to list or update your
user's group, call or write SYNTAX,

Salt Lake City, UTs R. Vincent
Hilton, 838 Emeril Ave., Salt Lake
City, UT 84116, 801/537-7149.

Montgomery, ILs Chris Kratsch,

1017 Harmony Dr., Montgomery, IL
60538.

Tacoma, WA: World Wide User Group
(Military personnel only), R.
Smith, POB 98682. Tacoma, WA
98498-0682.

Hazelwood, MO: McDonnell Douglas
Recreational Computer Club,
Timex/Sinclair SIG, J.B. Dann, 705
Utz Lane, Hazelwood, MO 63042.

Allendale, SC: Allendale County
Computer Users' Group, Gary West,
POB 345, Allendale, SC 29810.

Ypsilanti, MI: Add the title
TS1000.ZX81 Programmers Club to
last month's listing.

Monetevideo, Uruguay: Guillermo
Moyna, Mississippi 1634, Apt. 104,
Montevideo, Uruguay. Interested in
exchanging programs with any ZX/TS
programmer .

Dayton, OH: T/S Minds User Group,
Steve Douglas, 1515 Canfield Ave.,
Dayton, OH 45406, 513/278-8163.

Johnson City, NY: Wes Brzozowski,
Recording Sec'y, SINCUS, POB 36,
Johnson City, NY 13790.

San Antonio, TX: San Antonio
Timex/Sinclair User Group, James
Houston, 414 W. Elsmere, San
Antonio, TX 78212, 512/735-2895.

What's happened to the Nashua Area
Radio Club, 11 Briand Dr., Nashua,
NH 03063? Please contact SYNTAX if
you know this group's status.

11

DEAR EDITOR:

My Sinclair 16K RAM does not
work well with my ZX81; it takes
about four on/off warm-ups, only to
see black lines moving from bottom
to top on my screen.

Yerach Lazarovitz, Brooklyn, NY

Spring

Horizontal black bars drifting ver¬
tically on the screen result from
ripple in the 9V power pack. Your
power unit should read 9.75 VDC
650mA on the bottom. Those reading
500 mA are inadequate. If you have
the correct model, it may have
failed. Try another 9 VDC source
good for 650 mA or more. — KO

I found an error in _

Hacking £odg Your ZX81 by Toni
Baker. In Chapter 17, Toni gives
an incorrect address for two rou¬

tines used in floating point arith¬
metic. She calls them STACKA and
STACKBC, used to put numbers on the
calculator stack, and gives their
respective addresses as 1519 and
151C (hex). Correct addresses:

151D and 1520. The error appears
on pp. 159-162.

Kevin Bulgrien, Longview, TX

Other errors: on p. 158,

0.325 should read 0.375. On pp.
159-161, change CALL STACKA to
CD1D15. Change the top of p. 160
to the following: ADD 1755, SUB
174C, MULT 17C6 , DIV 1882. Make
corrections in the programs fol¬
lowing these items.

Clifford Efaw, Morton, WA

My ZX printer feeds paper
incorrectly since I bought it. I
corrected the problem after no¬
ticing the paper roller springs
were too weak. I increased their
tension by bending them forward
slightly, fixing the problem.

Wayne Johnston, San Francisco, CA

I printed this letter on a BROTHER
CE50 typewriter, after composing it with
my MEMOTEXT Word Processor . When I tried
to buy a CE50 typewriter to use with my
ZX81, a mail order house told me they knew
of no cable to fit my computer, even with
my MEMOPAK Centronics Interface.

After noticing that a CE50 interface
included the standard Centronics socket, I
knew I could use my interface and cable.

As you can see, my system gives me the
same capabilities of a much higher priced
system. Total cost to me: $800-900.

My only problem — locating daisy
wheels and ribbons.

John K. Mitchell, Westwood, MA

John also sent a copy printed
right- justified. — AZ

I typed a program from a book¬
let, More Software from Softsync,
into my TS1000 and it does not run.
I tried several fixes and still no
run. Please help.

Lenore J. Brown, Euclid, OH

Ken Currier of Softsync says the
program. Asteroids in Space, has no
bugs. Whenever you enter printed
programs, remember to enter key¬
words as keywords, not spelling
them out. Also use 0 (zero) in¬
stead of 0 (the letter) for num¬
bers. Some printed listings fail
to slash zeros, making them hard to
tell from the letter 0. — KO

When I listen to tapes I SAVE
on my Panasonic Slim Line recorder
(model RQ-2739) I hear loud static
noise in the background and in
empty areas between recording

1 2

starts and 5-second periods before
programs. I don't hear it using
four C batteries? only with the AC
power cord. I can't LOAD programs
I SAVEd. I can LOAD pre-recorded
programs using either power source.

Bob Wildschuetz, Florissant, MO

Though you do not say so, it sounds
like you get this problem only with
a 16K RAM pack attached. It's the
classic RAM noise or hum and should
go away if you use a Winky Board.
Alternatives include opening the
RAM pack and adding filtering to
the power lines — the noise origi¬
nates in the converter and feeds
back to the recording output. — KO

Here's a cheap and dirty meth¬
od to add reset to ZX/TS machines
for those who don't want to void
their warranty to add peripherals.
Take two solid #24 or smaller insu¬
lated wires attached to a push
button NO switch. Bare about 1/4"
of each wire, with the plug facing
you. Insert one wire between case
and prong 23. Tape it to the case
so it's out the way. The other
wire sits between the case and
prong 4B or 5B.

Clifford Efaw, Morton, WA

My 2K MicroAce with an added
8K ROM and video upgrade kit won't
work with my 32K Memopak. When I
turn it on, the screen remains
blank for about five seconds? then
a white line appears down the right
side of the screen. I built a
regulated power supply, cleaned and
tightened the edge connectors, and
removed the extra IK ROM and RAM
select ICs to no avail. Help!

Fred Schobert, Du Quoin, IL

MicroAce machines used selected Z80
chips, some of which run at Z80A
speeds. Adding more peripherals
can stop the Z80. Try changing to
a Z80A chip. — KO

I want to adapt my ZX81 RS232
board, printer and disk drive for
my 16K Spectrum. Can you help?

John Cipolletti, Southfield, MI

You face two problems: adapting
the connector and changing the
software or firmware for these
accessories. To make the connec¬
tions, simply wire an adaptor that
connects the ZX81-outputs of the
Spectrum to appropriate pins and
ignore the Spectrum outputs which
lack ZX81 counterparts. To correct
the software, track down the code
changes between ASCII (for Spec¬
trum) and ZX81 codes. Remember
that the Z80 codes are identical,
but the characters that produce
them differ. — KO

I like my TS1000 but not its
keyboard. Do you have information
about rewiring a standard keyboard
to fit the TS key matrix?

Carleton M. Hanson, Oshkosh, WI

SYNTAX published several articles
about wiring standard keyboards for
ZX/TS computers. See Syntax Quar¬
terly. Winter 82, for a complete
explanation, plus info on wiring
single-function keys. — KO

What is the difference between
a machine code compiler and a ma¬
chine code assembler?

Ramsay Daly, Seattle, WA

MC compilers turn a BASIC program,
or source code, into a machine-code
program, or object code. Assem¬
blers translate source code written
in machine code mnemonics one-for-
one into a machine-code program
(object code). In each case the
computer executes the object code
directly and continuously.

To complete the picture, the
ZX/TS BASIC interpreter translates
each line of BASIC the computer
runs, one at a time, into machine

13

language, executes that sequence,
and returns to examine the next
line. Hence we call BASIC an in¬
terpreted language.

By compiling programs, you
save the machine needing to in¬
terpret BASIC lines, thus your
program runs faster. — KO

I want to expand my system but
not sink a fortune into extra
equipment. What system would best
speed up load time and provide mass
storage? Will equipment and soft¬
ware now available work on new TS
computers the same as on my TS1000?
In particular, will current soft¬
ware work with a color-producing
TS? Finally, has Timex or Sinclair
considered using magnetic cards?

Ronald Sherard, Hays, KS

Your choices are fast-loading tapes
or disks. Tape systems offer bet¬
ter values although disks run fast¬
er. Mindware's system offers the
most reliability.

Yes, TS2040 printers work with
TS2068s? you don't need memory ex¬
pansions. Other devices need adap¬
tors. TS1000 software will run on
TS1500S, but not on color 2068s.

We presently know of no Timex,
Sinclair or third-party plan to use
magnetic cards. — KO

VENDOR REPORT AND NOTES

John Oliger still sells boards and
parts kits for his SQ articles.
Prices remain unchanged except for
a four-slot expansion board, $10
ppd. to replace the more expensive
larger board. John Oliger, 10115
Nassau Ln., Indianapolis, IN 46229.

Does your PSION Backgammon cassette
needs debugging? Timex is keeping
a list of users and expects to send
out revised versions after PSION
debugs the program. Lauren Esplin,
Correspondence Administrator, Timex
Computer Corp., Waterbury, CT
06720, 1-8 00-2 4 -TIMEX.

MACHINE CODE GRAPHICS DEMO

This program provides an un¬
usual display of machine code (MC)
graphics. It alters the I regis¬
ter, which contains the high order
address of the graphics table. I
discovered this trick while trying
to develop hi-res graphics for my
ZX81. By altering where the compu¬
ter thinks the graphics table is,
the program produces graphics sym¬
bols not normally seen by display¬
ing the bit patterns located at the
new addresses you set in line 20.

Try different messages in line
50, but don't exceed 31 characters.
To hold a screen, press BREAK. To
restart, press CONT and ENTER.

DELETE lines 40-70 and add
GOTO 1 for a high speed demo.

If you add these lines:

90 POKE 16515,30
100 RAND USR 16514
you can change the loop at line 10.

If you stop the program while
experimenting, you'll find the pro¬
gram lines are unreadable. To re¬
store to normal display (press
ENTER after each) :

EDIT

POKE 16515,30
RAND USR 16514

Clem Wehner, Scott AFB, IL

WHAT DOES THIS PROGRAM DO?

JL\l'

Billy Casebeer, Oologah, OK

14

BOOK REVIEW

Available from SYNTAX . . .

Title:

Author :
Publisher:

Price :

An Introduction to VU-
CALC Soreadsheetina for
the Timex/Sinclair 1000
and the Sinclair ZX81
Harry Anbarlian
McGraw-Hill Book Co.
1221 Ave. of Americas
New York , NY 10020
$22.95

"Run-out-and-r ip-off -a-user"
approaches affect all ZX/TS users,
(i.e., taped programs and printed
pages sold without regard for qual¬
ity or utility). One program that
does not belong in the "user use¬
less" piles: VU-CALC, a quick,
flexible matrix formatting program.

But one new book does belong
in the "useless" pile. An Intro¬
duction to VU-CALC Soreadsheetina
offers less actual information on
VU-CALC than the fanfold flyer that
comes with the program.

This book's cover looks good,
(possibly the book's best feature)
bearing all the appropriate TMs and
circled Rs to lend credibility to
its contents. The book offers five
"simple" and five "advanced" pro¬
grams presented in an undecipher¬
able manner.

Of the book's 251 pages, 191
contain the ten exercises presented
in this cryptic fashion. The first
50-odd pages discuss various as¬
pects of VU-CALC's use.

It appears the author expects
you to know and understand VU-CALC
commands (he explains none in the
text). But he does not expect you
to know how to press appropriate
keys (shown in the text by the
constant SHIFTS preceding addition
signs and use of the letter on each
key when describing commands or
functions) .

This example from page 56
typifies the overall approach:

"In addition to the above mentioned
commands the Vu-Calc Program has a
(D) DELETE FORMULA COMMAND and a
(G) GET and (S) SET COMMAND to move

For computing beginners —

Crash Course in Microcomputers $19.95

Covers hardware, machine language and
applications. Reviewed in SYNTAX, Oct. 1981.
Aad $1.50 shipping.

ZX80 Pocket Book $10.95

Includes ZX81 supplement. Covers Sinclair
BASIC, data and program listings.

Add $1.50 postage.

For advanced hardware/ software users —

Zilog’s Z80-Z80A CPU

Technical Manual $7.88

Zilog’s Assembly Language

Programming $15.75

Experiments in Artificial

Intelligence . $9.95

Add $1.50 postage.

SYNTAX back issues available, $4 each.

Call or write for our group subscription discounts.

SYNTAX • RD 2 Box 457 • Harvard, MA 01451
617 / 456-3661

a formula to any BOX you desire on
the spreadsheet. These commands
can be useful for your own individ¬
ual matrix creations and certainly
are well worth exploring, but are
not used in any of the matrix Exer¬
cises in this book."

These sentences constitute the
only mention of these important
commands (except in the index).
VU-CALC users should know that
these time-saving commands allow
you to move and alter formulas.

Another example: the only
definition of ABSOLUTE AND RELATIVE
options (an essential distinction
VU-CALC users must make): "You
will learn to use both ABSOLUTE
(where by using the $ a variable is
kept constant with no change) and
RELATIVE options together. Exam¬
ples of using the ABSOLUTE option
can be found in... (three of the
exercises). The RELATIVE option is
used in all the Exercises."

Gary West, Allendale, SC

15

SOFTWARE REVIEW

Program: ZX PRO/FILE

Price: $16.95 ($2 off for user

groups through Tom if
you send name, address
of each purchaser)
ROM/RAM required: 8K/16K minimum
Printed listings: Yes
Language: MC, BASIC

From: Thomas B. Woods

POB 64

Jefferson, NH 03583
Byte-Back, ROBOTEC

ZX PRO/FILE uses one of the
most sophisticated and efficient
data storage and retrieval systems
I ever expect to see for the ZX/TS.

This program stores data in
files from one or two characters up
to twelve 28-character lines. You
can chain files to store related
data in sequenced files. ZX PRO/
FILE does not automatically pre¬
determine file size, so you can mix
files of all sizes with no memory
waste. With 16K RAM you can store
10,980 characters.

Tom uses a quick, versatile
machine code search routine. You
can search files for any "word" up
to 28 characters. For instance,
you could search your address file
for "WOODS", "THOMAS" or "THOMAS B.
WOODS." You can search for two
words at once, allowing you to find
all the people named "WOODS" who
live in "NH" or everyone living on
"DORCHESTER ST." in "SPRINGFIELD."
You can number each file and output
in numerical order.

ZX PRO/FILE lets you define
print format for hard copy. You
can PRINT the entire file, any
specified line or block of lines.
You can specify the number of blank
lines between printed items. Al¬
though Woods wrote the program for
use with a printer connected with a
Memotech Centronics I/F interface,
two POKES allow the program to out¬
put to Timex and Sinclair printers
(explained in the manual).

FOR FASTER A EASIER DATA ENTRY
WITH YOUR E-Z KEYBOARD . . .

Here at last ts a large 60 Hey TACTILE
FEEL keyboard that plugs into the same
connectors as* the existing keyboard on
your ZX81 TIMEX/SINCLAIR 1000 or 1500

HERE THE CLICK ... FEEL THE SNAP!
lor every key pressed (tactile feedback)

IT S THE ONLY KEYBOARO WITH ALL OF
THESE FEATURES:

• 60 moving keys solid (not rubber)

NOT JUST A KEYBOARO REPLACEMENT
BUT AN ENHANCEMENT THAT GIVES
KEYBOARO FEATURES FOUND ONLY
ON MORE EXPENSIVE COMPUTERS

\

$84.95

90 day warranty

t you ll like it - 10 day return privilege on keyboarc

ZX PRO/FILE's 59-page manual
provides clear instructions for
program use. Other sections dis¬
cuss tailoring program use to com¬
mon applications, advanced file
manipulation techniques, a summary
of available search strategies, a
14-page description of how the
program works, and carefully anno¬
tated listings of BASIC and MC.

Woods also includes instruc¬
tions for program mods: compati¬
bility with FASTLOAD, providing a
tabulating capability for searches,
program adaption for 64K RAM, and
permitting files to trigger pro¬
grammed functions.

Drawbacks: I prefer a program

compatible with the TS2040 printer,
letting Centronics owners POKE. ZX
PRO/FILE could use an alphabetical
sorting routine, almost a necessity
in most data-handling applications.
ZX PRO/FILE's data storage format
takes some getting used to.

Joseph A. Grau, Midlothian, VA

16

INVENTORY — 8K/16K

INVENTORY helps you keep track
of household or business items.

Load 16K Syntactic Sum then
enter INVENTORY as listed. Any
keywords in PRINT or REM statements
are keywords — do not type them in
letter by letter. To type a key¬
word with the cursor in L (letter)
mode, type THEN (shift 3) — the
cursor now shows a K. Now press
the keyword — it appears on the
screen. Move the cursor to the
left, between THEN and the keyword.
DELETE the word THEN and the key¬
word remains. INVENTORY uses key¬
words and tokens to save memory in

these

lines

: 50,

255,

430,

500,

1029,

1245,

2015,

2025,

3015

, 3030

3070,

3200,

4015,

4025,

5015

, 5025

6015,

7000,

7020,

7330,

7500

, 8015

8025,

9000,

9010,

9690.

Spaces and graphics characters
form line 9800, the greeting after
a successful SAVE or LOAD.

When you get the correct Syn¬
tactic Sum, prepare to SAVE INVEN¬
TORY to tape. First press CLEAR
then ENTER. Next, enter:

LET AA=9500
Type in:

GOTO 9060

Start the recorder and press ENTER.
The program SAVES, then executes
GOTO AA (9500), which assigns the
variables and expands the DIMen-
sioned arrays to full size. In the
process, the computer reassigns AA
to 9800, bringing up the INVENTORY
graphic greeting when you SAVE or
LOAD the program in the future.

You see a graphic greeting and
a prompt to ENTER "M" FOR MENU.
Press M to bring up the Menu. Sel¬
ect any menu option by pressing the
corresponding key. If you make a
mistake and the program stops with
an error code, enter GOTO 100. Do
not RUN this program or you will
lose all variables and your data!

To start over again, enter CLEAR,
then GOTO 9500.

Follow the prompts to explore
INVENTORY. When you add items

(option 1) , INVENTORY allows these
inputs: catalog number, 8 alpha¬

numeric characters? description, 15
characters; source, 2 alphanumer-
ics; cost each 6 digits (decimal
point counts as one digit); on
hand, 3 digits; on order, 3 digits?
reorder, 2 digits. The last five
fields must contain numeric data
for the program to work correctly.

When you select option 2, the
program asks for the catalog number
of the item to DELETE. Enter it
with or without the leading zeros.
If the computer can match this num¬
ber with a previously entered item,
it displays the information on the
screen with a prompt to ENTER "D"

TO DELETE.

If you press D, the program
deletes the inventory item. If you
decide not to delete the item, just
press ENTER and the item remains.

To change an item's quantity
on hand, enter the catalog number,
then the amount sold or used. If
that amount exceeds the amount on
hand, the program tells you it can¬
not complete the transaction. If
your stock covers the sale, the
program automatically brings the
total up to date and displays it
with the new amount on hand.

In response to the TIME TO RE¬
ORDER prompt, or when ordering to
replenish existing stock, enter the
item's catalog number. After en¬
tering the amount ordered, you see
the ONORDER field updated.

When an order comes in, enter
the catalog number, then quantity
received. The program reduces the
ONDRDER amount and updates the ON
HA'ND and TOTAL for that item.

To VIEW an item in the inven¬
tory (option 6), enter the catalog
number. If the computer can't find
it, it displays RECORD NOT FOUND
and you may return to the Menu.

This program can LIST all
items held on file in order by
catalog number. Press 7 from the
Menu for LIST mode. For hard copy,
press Y, otherwise press N in an¬
swer to the prompt. If you choose

17

hard copy, the printer runs until
the computer finds the last catalog
number and sends all its data to
the printer. If you choose N, the
information appears on your screen;
press C to go to the next record.

Now press S to see the SUM¬
MARY. You see a list of the total
number of records on file, the
total quantity of all items ON
HAND, and the total value (total
amount held) of your inventory,
with the program name and last
update. If you want hard copy,
press Z and the computer COPYs the
SUMMARY to your printer.

Option 8 revises a record.
Enter the catalog number. The item
appears onscreen, with a cursor
after the CATALOG NUMBER field. To
change any data, just type the new
one and press ENTER. If you press
ENTER without typing new data, the
old data remains and the cursor
moves to the next line. If you
change the ON HAND or COST EAch
field, the TOTAL also changes.

REVISE also lets you recycle
space used by a DELETEd item. En¬
ter *DELETED to bring up the first
available deleted catalog number.
Input the changes in REVISE mode.

To SAVE, choose option 9 and
enter the date you want displayed
at the top of the Menu (up to eight
characters). The computer SAVES
the contents of INVENTORY to tape.
When the SAVE completes, you see
the first INVENTORY message again.

Brett McCarron, Olympia, WA

INVENTORY comes on tape with full
documentation for $10 from Medicine
Creek Productions, P. 0. Box 1184,
Olympia, WA 98507. For a list of
line and variable functions and
tips on modifying INVENTORY, send
an SASE to SYNTAX. — AZ

1 8

20

SOFTWARE REVIEW

Product: ZXMAN

Price: $14.95 + $2 C.O.D., $1.50

P&H if prepaid
ROM/RAM required? 8K/16K
Printed listings? No
Program listable? No
Language: Machine Code

From: Atto-Soft

832 E. Third St.
Galesburg, IL 61401
309/343-4114

Programmers who want to share
the profits from that ubiquitous
little arcade character who packs
away more quarters than ghosts seem
everywhere, judging from numerous
ads. ZXMAN represents one such
programmer's attempt (costing al¬
most 60 quarters).

After you LOAD the tape, this
machine-coded game first plays a
demo game if you do not take con¬
trol quickly — a fun-to-watch, in¬
formative routine.

ZXMAN presents a fast-moving
challenge. "Z", "X", "8" and "1"
represent ghosts. You can't spot
the ghosts as easily on black and
white screens as on color, but this
simply increases the need for close
attention (a clear example of ZX/TS
game-playing potential). Our
eight-year-old child stopped nag¬
ging for a more expensive computer,
partially from playing ZXMAN.

ZXMAN's creator designed the
program for use with a joystick,
like Atari's. (Atto-Soft sells
Atari joyticks for $14.95 + P&H.

See SYNTAX Jul.83 p.21 for a SUPER
(Atari) JOYSTICK hookup.— LFV) .

The joystick requires no modifica¬
tion. Installation involves open¬
ing your computer and soldering six
wires to the keyboard sockets.
Atto-Soft provides clear directions
and also gives suggestions for oth¬
er joystick uses. I wired a 14-pin
DIP socket in parallel with the
keyboard and can unplug the joy¬
stick when not using it — useful be¬
cause the joystick locks out some

shifted com-mands , such as GRAPHICS.
You can play ZXMAN without a joy¬
stick using "5" as fire and "1-4"
to move the "hero." Of course,
using the joystick adds to the fun.

Atto-Soft experienced some
distribution problems with early
deliveries about six to eight
months ago, due to premature adver¬
tising. This problem seems solved:
My noisy first tape refused to LOAD
and Atto-Soft promptly sent a re¬
placement that RUNS and LOADS with¬
out a hitch. (Atto-Soft took over
the distribution, resulting in
problem-free delivery, says Atto-
Soft co-owner Keith Ennis. — LFV)

Ronald Miller, Murrysville, PA

LATE NEWS: Laserscan wants to
liquidate their limited 16K RAM kit
stock — regular $54.95 now $16.00+
$2.95 P&H. Kits contain all parts
and instructions except memory
chips; you'll need eight 4116-200ns
dynamic RAM chips (about $12.95 for
all, says Dennis Hawkins of Laser-
scan). For info or orders, send an
SASE or call Laserscan Electronics
Corp, 2305 Broadway, Riviera Beach,
FL 33404, 305/842-4255.

ADDRESSING — A BRIEF TUTORIAL

If you find ROM, RAM & PORT
addressing and decoding confusing,
here's some explanation of what's
what. Except in the diagram, here
we call control lines by name with¬
out distinguishing RD and NOT READ.
On the schematic, a line over the
name XX means negation NOT XX.

Each address includes a number
and several control signals? equal
numbers specify separate locations
if the control signals differ. Z80
CPUs use a 16-bit address buss — 16
wires that can assume 65536 permu¬
tations of 0 and 5V — as well as 13
control lines that we can combine.
But only MREQ & IORQ are usually
used to create different addresses.

Decoding an address means to
create circuitry to select a device

21

based on both numeric and control
addresses. Full decoding chooses
an exact permutation. Not fully
decoded, or partial decoding, means
ignore some bits and control lines
and respond based on the rest. In
either case, the circuit combines
address signals to form a few con¬
trol signals for our device. For
example, RAM CS combines MREQ and
A14 ' in a ZX/TS.

All partially decoded schemes
respond to many addresses. So if
you PEEK 1 or PEEK (1+8192) on your
ZX/TS, you get 253 because the ROM
isn't fully decoded. You can leave
your 16K ZX/TS pack on to try this,
but a 64K gives different answers —
it's fully decoded.

IORQ & MREQ differentiate port
or memory requests of Z80 addresses
0-255. IORQ indicates that the CPU
will communicate with the location
whose number is on the buss and
process the data as to or from a
PORT. MREQ tells your decoder the
CPU will process the data for this
location as though it were to or
from MEMORY. See the Zilog CPU
Technical Manual for details.

RD and WR separate the ReaD
and WRite operations — but you may
also use them in the address.

Thus you can read port 254 &
have it be the keyboard, a read¬
only device, and write to port 254
& have it be the display, a write-
only device. These expect IORQ to
be selected. But ROM location 254
responds to 254 and RD and MREQ.

You could then assign a write-only
device at 254 and MREQ and WR. — KO

Sinclair computers expect the
address lines A0-A7 each to control
one device, treated as a port. A
device responds when its line (Ax)
is 0 during IORQ. Each device
reacts to 128 addresses; only one
is proper. This specific form of
partial decoding is not recognized
in the notes by Paul Donnelly and
KO in SYNTAX Aug. 83. To access one
device keep A0-A7 high except for
the ONE that selects it.

AAAAAAAA ADDRESS PORT
76543210 HEX DEC DEVICE

11111111 FF 255 DISPLAY **
11111110 FE 254 KBD , CASS *
11111101 FD 253 DISPLAY
11111011 FB 251 PRINTER
11110111 F7 247 RESERVED
11101111 EF 239 RESERVED
11011111 DF 223 RESERVED
10111111 BF 191 USER ASSIGN
01111111 7F 127 USER ASSIGN

* This port is fully decoded.

** Used for speaker and border in
the ZX Spectrum.

According to the SPECTRUM manual,
bits A6 & A7 are ignored; you can
use them. For 512 more addresses,
use register indirect addressing of
the port. Take any permutation of
A8-A15 with either USER ASSIGN I/O
address preceding. Use opcodes:

LD BC,portaddr ;portaddr=**7FH or

;**BFH. 00<**<FF

OUT (C) ,r ;write to ** from r

IN r,(C) ;read from ** to r

Or use partial decoding again
with A8-A15 to let one gate access
both of Paul's devices. Use A14 &
A15 as the single low bit to read
from two external devices as shown
in the sample circuit. One device
is port 7FBF & device 2 is at BFBF.
Just 3/4 of another chip can decode
the write function. I recommend
using a 74LS32 Quad OR gate because
of its lower power requirement and
better availability.

Robert P. La Jeunesse,
Ann Arbor, MI

Each gate uses 1/4 74LS32

22

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